Cathodic protection apparatus

ABSTRACT

1,153,007. Cathodic protection. INTERNATIONAL HARVESTER CO. Aug.3, 1966 [Aug.30, 1965], No.34728/66. Heading C7E. A cathodic protection anode having a centred, blind, non-circular hole therein (so that it can grip a removal tool) is screwed into a plug, with a centered hole, which is screwed into a threaded plug bore in a fluid holding vessel. The hole in the anode penetrates thereinto to such an extent that depletion of the anode will open it to create an escape path for a depletion-signalling leakage stream, the appearance of which indicates that the anode must be changed, the removal of the residue from the plug being accomplished by a wrench using the non-circular hole. In an example the vessel is of Al, the cover into which the plug is screwed is of gray cast iron, the plug is of brass and the anode of zinc.

Jan. 21, 1969 EFTAUgK 3,423,305

CATHODIC PROTECTION APPARATUS Filed Aug. 30, 1965 United States Patent 3 Claims ABSTRACT OF THE DISCLOSURE Anode for cathodic protection having an internal blind opening concentric to the longitudinal axis of the anode, and penetrating through the head and body to a point such that depletion of the major portion of the anode, opens the blind end so that it becomes a nozzle to signal depletion with a thin jet of leakage water.

The present application relates to the cathodic protection, against electrolytic corrosion, of metals subjected to raw Water, e.g., sea water. It more particularly relates to a means for introducing a length of sacrificial anode metal within a metal vessel, the anode being on the raw water side thereof and electrically coupled to the structure for rendering the metal structure within the vessel electrically passive.

The difficulty with internally-mounted sacrificial metal, referred :to in one specific form as a pencil anode, or more generally as a zinc, is that the depletion rate cannot be observed. Therefore, zincs are sometimes completely consumed and, without the protection thereof, metal structure in the vessel starts corroding, ultimately resulting in a failure within the vessel. The procedure of periodic changes of the zincs is no complete answer to the problem, and the difficulty of that procedure is that useable zinc is unnecessarily discarded and, moreover, the periodic replacement can prove to be unnecessary work.

The foregoing difficulties are materially reduced or substantially eliminated by my inventions of a depletionsignalling method and an improved anode device, as will now be explained. Features, objects, and advantages of these inventions will either be specifically pointed out or become apparent when, fora better understanding, reference is made to the following written description, taken in conjunction with the accompanying drawing which shows a preferred embodiment thereof and in which:

FIGURE 1 is an exploded isometric view of a fluidtight vessel embodying the present invention;

FIGURES 2 and 3 are longitudinal elevational and outer-end elevational views, respectively, of my anode device;

FIGURE 4 is similar to FIGURE 2, but shows the depleted device in operation, providing a path for a depletion-signalling stream of raw water; and

FIGURE 5 is similar to FIGURE 2, but shows a modified form of my device.

More particularly in FIGURE 1 of the drawing, the cathodically-protected vessel selected .as an illustrative example forms both the expansion tank and the water-towater heat exchanger for a marine diesel engine, not shown. The hot engine cooling water'enters into, and is discharged from, the vessel 10 through a path indicated by the consecutive arrows 12. An exchanger tube bundle 14 is disposed transversely across the path 12 and communicates with an inlet 16 and an outlet 18 so as to conduct ambient-temperature, raw water internally of the bundle. An end cover 20 at one end of the tube bundle 14 cooperatively fits over a partition 22 which separates the inlet and outlet raw water, and the cover 20 is bolted to the vessel 10 by means of hold-down bolts passed through flange openings 24 on the latter.

A neck portion 26 projecting laterally from the side- 3,423,305 Patented Jan. 21, 1969 wall of the end cover 20 receives an anode structure 28a. The structure 28a has a bleed hole 30 in the center constituting a depletion signalling blind opening.

The anode structure 28a projects inside the cover 20 on the vessel 10. It provides an internal length of sacrificial metal which is not perceptible from the outside and which is preferably disposed across and closely adjacent to the inlet 16 so as immediately to encounter the ions in the water which otherwise would create local action .and corrosion of the metal structure.

In FIGURE 2, the anode or body 32 of the structure 28a is shown in one conventional form, being in the shape of a rod of the sacrificial metal. The body is electrically coupled by means of a double-threaded, copper-alloy head or plug 34 to the neck portion 26 of the sidewall of the end cover 20. A plug bore 36 within the neck holds the plug 34 of the structure 28a watertight in threads which taper inwardly. The body 32. is threaded into an anode bore formed within the plug 34 and the threads taper outwardly at 38. The plug 34 is readily removed by unthreading it from the bore 36 in the longitudinally outward direction, and the diameter of the body 32 is smaller than the plug bore 36 and thus is removed with the plug. The plug 34 is shown to have a hex-head, to accommodate a standard crescent or socket wrench.

The body 32 prevents the bleed hole 30 from communicating with the raw water 40 in the vessel. Although the bleed hole can be series drilled after the plug and body parts are joined together, it is preferable to preform the hole in each part separately, the portion 42 thereof which extends into the body 32 penetrating to a point slightly beyond the inner end of the plug 34 and the threads on the body 32.

As seen in FIGURES 3 and 4, raw water freely escapes as a depletion-signalling, leakage stream through the bleed hole or blind opening 30, as soon as the body 32 has dissipated sufliciently to open :the blind end of the blind opening. In practice, the engine operator will probably insert a make-shift stopper in the hole 30 until the engine is shut down, whereupon he will replace the structure 28a with a fresh structure so that there is no material discontinuity in cathodically protecting the vessel internally. Either the entire structure 28a can be replaced or, if it is desired to reuse the plug 34, the remaining portion of the previous body 32 is removed and a new body is reinserted in the plug 34. For this reason, the portion 42 of the hole can be of a non-circular cross section to grip a removal tool such as an Allen wrench.

In the embodiment of FIGURE 5, the structure 28b has the body 32 and the plug 34 thereof integrally joined and made of the same sacrificial anode metal. The entire structure 2812 must be replaced after the blind hole 30 begins to discharge a depletion-signalling leakage stream of the raw water 40.

The body 32 is made of a metal selected from the electro-motive series which will be electro-positive to the other metal or metals involved. Thus, the sacrificial metal can be zinc, magnesium, or a magnesium alloy, and so forth, where zinc is preferable because it is the most commonly used and convenient sacrificial metal. Zinc is less noble with respect to all of the common constructional metals such as iron, steel, cooper, tin, brass and bronze.

Following is an example of the specifications for an installation embodying the present inventions:

Vessel 10 Aluminum Bundle 14 Copper Cover 20 Gray iron Plug in structure 28a Brass Body 32 Zinc Bleed hole 30 A3" diameter Bleed hole 30 1 /2" depth From an examination of FIGURE 1, it can be appreciated that a novel method is herein provided for assuring the presence of zinc within the vessel 10. When the body is consumed for its major part, a thin telltale stream of raw water emits in a perceptible way through the hole 30, due to the slight internal pressure maintained within the vessel 10 by the raw water pump, not shown. The leakage, if not stopped by the engine operator, is of minor consequence and, anyway, the zinc is preferably replaced immediately upon engine shut-down.

What is claimed is:

1. A fiuid holding vessel having an anode-receiving portion formed with a plug bore;

a plug threaded in the bore and formed with an anode bore in the plug;

a sacrificial anode threaded in the anode bore; and

means forming a centered blind opening through the plug and into the anode comprising series aligned holes in the respective plug and anode, the hole in the latter of which being of an appropriate noncircularity in cross section to grip a removal tool, and penetrating to a point therein such that depleting the anode to that point opens the blind end of the opening, creating the escape path for a depletion signaling, leakage stream therethrough, and opening the hole in the anode to access by :wrench for removal to replace same.

2. A vessel holding copper heat exchange tubing and having an anode receiving portion formed with a plug bore;

a copper alloy plug threaded in the bore and formed with an anode bore in the plug;

a zinc anode threaded in the anode bore; and

means forming a centered blind opening through the plug and into the anode comprising series aligned holes in the respective plug and anode, the hole in the latter of which being of an appropriate non-circularity in cross-section to grip a removal tool, and penetrating to a point therein such that depleting the anode to that point opens the blind end of the opening, creating the escape path for a depletion signaling leakage stream therethrough diverted from the copper tubing, and opening the hole in the anode to access by wrench for removal to replace same.

3. The invention of claim 2, said anode receiving portion comprising a gray iron portion, said plug having external threads by which it is threaded into the plug bore within the gray iron portion, the parts of the plug and anode inwardly of the external threads being no larger than said external threads whereby the parts may be inserted through the plug bore and form an electrical coupling to said gray iron portion.

References Cited UNITED STATES PATENTS 852,466 5/1907 Stewart 204-197 901,809 10/1908 Harris et al 204-197 2,609,340 9/1952 McMahon et al 204197 2,784,156 3/1957 Maurin 204-197 2,805,987 9/1957 Thorn et al 204-197 OTHER REFERENCES Supplement to the use of Magnesium Anodes for the Prevention of Corrosion in Water Heaters and Hot Water Storage Tanks, The Dow Chemical Co., Class A No. 44545, Feb. 10, 1947, FIGURE 8.

ROBERT K. MIHALEK, Primary Examiner.

T. TUNG, Assistant Examiner.

US. Cl. X.R. 

